Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true and destructiveHint=false, yet the description still adds real value: it discloses that seller-supplied fields are untrusted prompt-injection surface and instructs the agent to report rather than follow them, plus the notable absence of seller information. It says nothing about auth or rate limits, so not a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The content is well front-loaded (return fields first, call condition second, safety note last), but the entire text is duplicated verbatim in English and French, roughly doubling the token cost for an agent that reads either version. The redundancy is defensible for localization but still dilutes conciseness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema present the description need not explain return values, yet it still enumerates the payload, gives the call condition, and covers the untrusted-content handling that no structured field carries. Nothing an agent needs to invoke this correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so both slug and language are already documented, including the enum and default. The description adds only provenance for slug ('from search_ads'), which the schema also states, so this sits at the baseline for a fully-covered schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Returns one ad in full') and enumerates the returned payload, which cleanly separates it from search_ads (plural listing) and similar_ads. An agent can identify the tool's role without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit trigger ('when the user wants more about one ad') and names the source of the required argument (a slug from search_ads). It never distinguishes itself from similar_ads, which is the one plausible alternative, so it falls short of full when/when-not routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.